Hydraulic electromechanical transducer



1951 A. L. w. WILLIAMS 2,565,158

' HYDRAULIC ELECTROMECHANICAL TRANSDUCER Filed Aug. 11, 1947 RADIO TRANSMITTER o 2! RADIO RECEIVER INVENTOR. ALFRED L.W. WILLIAMS Patented Aug. 2 1, 1951 HYDRAULIC ELECTROMECHANICAL TRANSDUCER Alfred Leslie W. Williams, Cleveland Heights,

Ohio, assignor to The Brush Development Company, Cleveland, Ohio, a corporation of Ohio Application August 11, 1947, Serial No. 767,987

19 Claims.

The subject matter of this invention relates generally to electro-mechanical devices for transducing between electrical and mechanical energy, or vice versa. The invention more particularly relates to transducers of the electro-mechanical type in which acoustical energy is utilized or produced by the transducer, and in a.

specific form the invention relates to transducers of the type under consideration in which are used levers of the hydraulic type. The acoustical or hydraulic energy which is transduced to or from electrical energy in the devices of the invention may be associated with displacements or vibrations of any suitable acoustical or hydraulic medium capable of transmitting elastic-wave energy or hydrostatic pressure. As used in the specification and in the accompanying claims, the term acoustical has the broad significance usual in the art and refers to ultrasonic as well as to audible sound phenomena.

Electro-mechanical devices for transducing between electrical and mechanical energy, or vice versa, are well known in the art. Thus transducers comprising an electro-mechanical actuating element of Rochelle salt have been widely used, both in microphones and in receivers. In transducers of the type under consideration, rather high forces but rather small movements are involved in the actuating element. Therefore, it has been the practice, in many such prior transducers, to provide a lever arrangement for converting the small movement involved in the actuating element to a large. movement which is used, or for converting small forces which are available into large forces operating upon the actuating element of the transducer.

Also, actuating elements for electro-mechanical transducers which operate both in the transverse mode and in the longitudinal mode, with reference to the associated electrical field, are known in the art. Thus in the copending application for United States Letters Patent of Hans Jafie, Serial No. 740,460, filed April 9, 1947, there is described and claimed a transducer. element comprising a body of dielectric material which may, for example, be barium titanate. When properly polarized to respond in a linear manner to the fundamental component of an alternating field applied thereto, such a transducer element has associated with an applied electric field a motion in the direction of the electric field and a motion transverse to the electric field. The magnitudes of these efiects are such as to render actuating elements of the type. under consideration capable of many uses as the actuating elements of electro-mechanical transducers. However, in general, the way in which actuating elements of barium titanate, as well as substantially all other actuating elements of electro-mechanical transducers, have been used in commercial transducers has been such that only one of the above-mentioned modes inherent in the material has been utilized. It would be very desirable, therefore, to provide an electromechanical transducer in which each of the above-mentioned modes were utilized.

It is an object of the present invention to provide an improved electro-mechanical device for transducing between the types of energy which are classified as electrical and mechanical.

It is another object of the invention to provide an electro-mechanical transducer which is not subj ct to one or more of the above-mentioned disadvantages of prior such devices.

It is still another object of the invention to provide an electro-mechanical transducer in which more than one electro-mechanical transducing mode of the actuating element is utilized.

It is a further object of the invention to provide a new and improved elcctro-mechanical transducer utilizing the coupling between an electro-mechanically sensitive material and a contiguous acoustical or hydraulic medium for translating mechanical or mechano-acoustical energy.

In accordance with one feature of the invention, an electro-mechanical transducer comprises hollow means having an inside surface and an outside surface defining walls the major portions of which are of polycrystalline dielectric material of the type capable of developing substantial mechanical strains when subjected to electrostatic fields. The transducer also includes means for coupling only one of these surfaces effectively to a medium capable of transmitting-hydrostatic pressure for translation of acoustical energy between the afore-mentioned walls and the medium. Additionally the transducer comprises electrode means on each side of the wall portions of the polycrystalline dielectric material for translating the electrical currents associated with the transducing between acoustical energy in the medium and electrical energy in the wall portions.

In accordance with another feature of the invention, an electro-mechanical device for transducing between the types of energy which are classified as electricaland mechanical comprises a container having at least one wall portion which is provided with means for translating electrical currents associated with an electric field across that wall portion and which has the property of transducing energy between the two abovetioned types. The device also includes a fluid in the container and a mechanical-acoustical coupling extending through a 'wall of the container and acoustically coupled to the fluid; this coupling ordinarily takes the form of a piston acting upon the fluid in the container. Means also are provided, including the above-mentioned means for translating electrical currents and the piston, for appbing energy of one of the abovementioned types to the wall portion and for deriving energy or the other of the above-mentioned types therefrom.

For a better understanding of the present invention, together with other and further obiects thereof, reference is had to the following description taken in connection with the accompanyingdrawinganditsscopewillbepointed out in the appended claims.

Referring now to the drawings. Fig. 1 illustrates an electro-mechanical transducer in accordance with the invention which is utilized as a microphone; Fig. 2 illustrates the electromechanical transducing properties oi. a wall portion of the transducer of Fig. 1; Fig. 3 illustrates a modified form or the transducer arrangement of the invention which is utilized to actuate a speaker; and Pig. 4 illustratu a modification of the invention in which the transducer actuating elements are electroded fiat plates.

Referring now to the drawing, in Pig. 1 there is illuustrated an electro-mechanical device is for transducing between the types oi energy which are classified as electrical and mechanical. As shown. the device is such as to transduce mechanicalenergytcelectrical energy. Thedevicecomprises aninclosingmeans or container ll,which has at least one wall portion provided with means for translating or conducting electrical currents associated with an electric-field across the wall portion,andwhichhasthepropertyoftransduc- .ample, be oil. Extending through the upper wall portion of thecontaineris amechanical-acousticalcouplingin'theformofapiston lthebottomof whichisacousticallyeoupledto'the liquidmediumll. Thepiston'liactsuponthefluid fortranslatingmechanicalenergytothewallportions of thecontainer. Thewallportionsofthe container are provided with an inside electrode i4 and an outside electrode respectivelyofthecylinder. and ll,adiacent these two surfacesontheoppositesidesoi'thewallsofthecontainerll,are separated or electrically insulated from each other at all points. A diaphragm II, which is shown schematically,isutiliaedasthe diaphragm ofamicrophoneinordertoapply mechanical ento electrode i4 and by a conductor is connected to electrode II, to the input circuit of a radio transmitter II. v

In order to polarize the titanate material. in the manner fully described in the above-mentioned copending application of Hans Jafle, a uni-directional source of potential II is coupled across electrodes H, II through a resistor 22. However, in some cases, materials such as titanates have the property of retaining polarization after a uni-directional field has been applied thereto so that the material responds in the fundamental mode, that is, in an essentially linear manner, to an alternating field applied thereto and, in case material of this type is utilized, the source of voltage Il may be omitted. A coupling condenser II is utilized to isolate the source Ii from the input circuit of radio transmitter II. The container H is mounted upon some stationany object (not shown) which is fixed relative to the mounting member to which the rim of diaphragm I1 is affixed.

Considering now the operation of the embodiment of the invention described in Fig. 1. it will be seen that vibratory forces are applied to the piston II when the diaphragm I1 is actuated and that the piston It acts upon the fiuid i2 inthe container II to apply mechanical forces to the walls of the container. Thus the mechanical energy applied to the piston is translated through the bottom of the piston into the fluid II, which translates the energy as acoustical energy to the walls of the container. The fiuid II inside the container and-the fluid-tight closure provided by the walls of the container and around the piston constitute means for coupling only the inside surface of the container eifectively to a medium capable of transmitting hydrostatic pressure. Due to the transducing properties of the material ll of the container, corresponding electrical sisnals are developed and applied to the input circult of transmitter II, the electrical currents associated with the transducing being translated by electrodes II and II. In Fig.2 is illustrated one portion of the container II. This may, for example, comprise the bottom of the cylindrical container. If a portion of properly polarised barium titanate material of the type illustrated in Fig. 2 has an electrical potential of a certain polarity applied between the upper and lower faces thereof, the material tends to expand in all radial directions as illustrated by the arrows If, II, ll, 2!, and 2t and tends to contract in its direction as indicated by the arrows 21. ll. Referringtol igure Litwillbeseenthat forces of the type represented by the arrows 22 to It inclusive are applied to the bottom section of the container II when the piston It is actuated in a downward direction. This means that the forces which are so applied to the walls of the container are accumulatively effective in causing corresponding electrical potentials to appear at electrode ll, II since the effect described above is visible. It is for this reason that the present invention is of particular utility when utilized with transducers including actuating elements of titanate material.

In Fig. 3 there is illustrated-an embodiment of the invention in which the transducer is utilized to convert electrical energy into mechanical energy. Specifically. the transducer or Fig. 3 is used ergytoapiston lloperatingontheliquidinthe 1| tocausetheelectrical outputofaradioreceiver g 34 and 35.

to drive a diaphragm acting as a loudspeaker. Circuit elements of Fig. 3 which are similar to those of Fig. I bear similar reference numerals in the 30-series. Thus the Fig. 3 arrangement com rises a container 30 which is in the form of a hollow fiphere having wall portions 8| and filled with a liquid 32. An inside electrode 24 and an outside electrode 35 are provided for the container and a piston 36, operating through the wall of the sphere upon the liquid 32, is effective to apply mechanical movements of the wall portions of the sphere 3! to the diaphragm 81. Conductors 38 and 39 are utilized to connect the inside electrode 34 and the outside electrode 35 to the output terminals of the radio receiver 48. As in the case of Fi ure 1, the battery 2i and resistor 22 may be utilized in cases where it is necessary to polarize the material of the sphere 3| in order to provide a linear response in the manner explained in full in the above-identified Jaife application. a

The operation of the element of Fig. 3 will be readily apparent from the description which has been given above with reference to the operation of the Fig. 1 arrangement. Specifically, however, radio signals which are received by the receiver 40 are detected in order to obtain the audio components of the received signals which are applied, through conductors 38 and 39, to the electrodes These varying audio signals cause variations in the pressure which the wall Dortions of sphere 3| apply to the piston 36 through the liquid 32 which fllls the entire container. These pressure variations upon piston 88 are applied through the drive member to the diaphragm 31 where they are converted into audible sounds.

In Fig. 4 is illustrated an embodiment of the invention in which the liquid-filled container is formed by a construction consisting of a number of electroded slabs of material eil'ective to transduce mechanical energy to electrical energy, or vice versa. Thus the container may be constructed of slabs 42, 43, A l, and I! enclosing the left-hand and right-hand sides, the top and the bottom of the container as illustrated. and additional slab 46 and another slab (not shown) may be utilized to enclose the back and front end portions, respectively. The piston 41, represented schematically by the reference numeral 41, operates through the wall portion of the container formed by the slab 44. The operation of the embodiment of Fig. 4 as the actuating element of a microphone will be readily understood with the description which is given above with reference to Fig. 1 and its operation as an actuating element of a speaker will be readily understood from the description which has been given above with reference to the Fig. 3 embodiment of the invention. 1

The actuating element which has been described with reference to each of the arrangemerits of Figs. 1, 3 and 4 is such that substantially all wall portions of the container are electroded and are thereby effective as transducer portions of the element. It will be understood, however, that it is not necessary that all the wall portions of the container be electroded inasmuch as a useful output may be derived from the actuating element from any electroded portion of the container. In general, however, it is advantageous to electrode all available wall portions for the reason that the transducing capabilities of the device are thereby increased.

While there have been described what are a present considered to be the preferred embodiaromas ments of the invention, it will be obvious to those skilled in the art that various changes and modiflcatlons may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit vided with means for translating electrical cur-' rents associated with an electric field across said wall portion and which has the property of transducing energy between the two above-mentioned types; a fluid in said container; a piston acting upon said fluid in said container; and means, including said means for translating said electrical currents and said piston, for applying energy of one of said types to said wall portion and for deriving energy of the other of said types therefrom.

2. An electro-mechanical device for transducing mechanical energy to electrical energy comprising; a container having at least one wall portion provided with means for translating electrical currents associated with an electric fleld across said wall portion and which has the property of transducing mechanical energy to electrical energy; a fluid in said container; a piston acting on said fluid in said container for applying mechanical energy to said wall portion; and means, including said means for translating said electrical currents and said piston, for applying mechanical energy to said wall portion and for deriving electrical energy therefrom.

3. An electro-mechanical device for transducing electrical energy to mechanical energy comprising; a container having at least one wall portion provided with a means for applying an electric fleld thereto and which has the property of transducing electrical energy to mechancal energy; a fluid in said container; a piston acting upon said fluid in said container for receiving mechanical energy from said wall portion; and means, including said means for applying an electric field to said wall portion and said piston, for applying electrical energy to said wall portion and for receiving mechanical energy therefrom.

4. An electro-mechanical device for transducing between the types of energy which are classified as electrical and mechanical comprising; a cylinder having wall portions provided with means for translating electrical currents assc ciated with an electric field across said wall portions, which wall portions have the property of transducing between the two above-mentioned types; a fluid in said cylinder; a piston in said cylinder acting upon said fluid and means. including said means for translating said electrical currents and said piston, for applying ener y of one of said types to the wall portions of said cylinder and for deriving energy of the other of said ty-pes therefrom.

5. An electro-mechanical device for transducing between the types of energy which are classified as electrical and mechanical comprising; a hollow sphere provided with means for translating electrical currents associated with an electric field across the wall thereof, which wall has the property of transducing. energy between the two above-mentioned types; a fluid in said sphere; and a piston in a wall portion of said sphere and acting upon said fluid and means, including said 7 means for translating said electrical currents and said piston, for applying enem of one of said types to the wall of said sphere and for receiving energy of the other of said types therefrom.

8. An electro-mechanical device for transducing between the types of energy which are classifled as electrical and mechanical comprisin a container having at least one wall portion of barium titanate material provided with means for translating electrical currents associated with an electric field across said wall portion and which has the property of transducing energy between the two above-mentioned types; a fluid in said container; a piston acting upon said fluid and means, including said means for translating said electrical currents and said piston, for applying energy of one of said types to said wall portion and for deriving energy of the other of said types therefrom.

7. An electro-mechanical device for transducing between the types of energy which are classifled as electrical and mechanical comprising; a container having at least one wall portion of barium titanate which includes a substantial amount of strontium titanate and provided with means for translating electrical currents associated with an electric field across said wall portion, said wall portion having the property of transducing energy between the two above-mentioned types; a fluid in said container; a piston acting upon said fluid and means, including said means for translating said electrical currents and said piston, for applyingenergy of one of said types to said wall portion andfor deriving energy of the other of said types therefrom.

8. An electro-mechanical transducer compris ing: hollow means having an inside surface and an outside surface and substantially all wall portions of which are of polycrystalline dielectric material of the type capable of developing substantial mechanical strains when subjected to electrostatic fields, means for coupling only one of said inside and outside surfaces effectively to a medium capable of transmitting hydrostatic pressure for translation of acoustical energy between said one surface and said medium, and electrode means on each side of substantially all of said wall portions of dielectric material for translating the electrical currents associated with the transducing between acoustical energy in said medium and electrical energy in said wall portions.

.9. An electro-mechanical transducer comprising: inclosing means of polycrystalline dielectric material of the type capable of developing substantial mechanical strains when subjected to electrostatic fields and having a generaly cylindrical inside surface and a generally cylindrical outside surface substantially concentric with said inside surface, means for coupling effectively only one of said generally cylindrical inside and outside surfaces of said inclosing means to a medium capable of transmitting hydrostatic pressure for translation of acoustical energy between said one surface and said medium, and electrode means on each of said insid and outside surfaces for translating the electrical currents associated with the transducing between acoustical energy in said medium and electrical energy in said dielectric material.

10. An electro-mechanical transducer comprising: inclosing means having an inside surface and an outside surface and having at least one wall portion of polycrystalline-dielectric material of the type capable of developing substantial mechanical strains when subjected to electrostatic flelds, means for coupling only said inside surface efl'ectively to a medium capable of transmitting hydrostatic pressure for translation of acoustical energy between said inside surface and said medium, and electrode means on each side of said wall portion for translating the electrical currents associated with the transducing between acoustical energy in said medium and electrical energy in said wall portion.

11. An electro-mechanical transducer comprising: inclosing means having an inside surface and an outside surface and having at least one wall portion of polycrystalline dielectric material of the type capable of developing substantial mechanical strains when subjected to electrostatic flelds, means for coupling only said inside surface effectively to a medium capable of transmitting hydrostatic pressure for translation of acoustical energy between said inside surface and said medium, electrode means on each side of said wall portion for translating the electrical currents associated with the transducing between acoustical energyin said medium and electrical energy in said wall portion, and a mechanicalacoustical coupling extending through a wall portion of said inclosing means and acoustically coupled to said medium.

12. An electro-mechanical device for transducing between the types of energy which are classified as electrical and mechanical comprising: inclosing means having an inside surfac andan outside surface and having at least one wall portion of polycrystalline dielectric materialof the type capable of developing substantial mechanical strains when subjected to electrostatic fields; means for coupling only said inside surface effectively to a medium capableof transmitting hydrostatic pressure for translation of acoustical energy between said insidesurface and said medium; electrode means on each side of said wall portion for translating the electrical currents associated with the transducing between acoustical energy in said medium and electrical energy in r said wall portion; a mechanical-acoustical coupling extending through a wall portion of said inclosing means and acoustically coupled to said medium; and means, including said electrode means and said mechanical-acoustical coupling,

for applying energy of one of said types to said wall portion and for deriving energy of the other of said types therefrom.

13. An electro-mechanical transducer comprising: inclosing means having an inside surface and an outside surface and substantially all wall portions of which are of material having the v property of transducing between electrical and mechanical energy, means for coupling only said inside surface effectively to a medium capable of transmitting hydrostatic pressure for translation of acoustical energy between said inside surface and said medium, electrode means on each side of substantially all of said wall portions for translating the electrical currents associated with the transducing between acoustical energy in said medium and electricalenergy in said wall portion, and a mechanical-acoustical coupling extending through a wall portion of said inclosing means and acoustically coupled to said medium.

14. An electro-mechanical transducer comprising: a container having an inside surface and an outside surface and having at least one wall portion comprising a piezoelectric material which has the property of transducing between electricalandmechanicalenergy,afluidinsaidcontainer and coupled effectively to only said inside surface thereof for translation of acoustical energy between said inside surface and said fluid, electrodes on each side of said wall portion for translating the electrical currents associated with the transducing between acoustical energy in said fluid and electrical energy in said wall portion, a mechanical-acoustical coupling extending through a wall portion of said container and acoustically coupled to said fluid, and means connected to said mechanical-acoustical coupling externally of said container and effectively uncoupled from said outside surface thereof for translating the mechanical energy associated with motion of said mechanical-acoustical coupling.

15. An electro-mechanical device for transducing between the types of energy which are classified as electrical and mechanical comprising: a container having an inside surface and an outside surface and having at least one wall portion which is provided with electrodes and which has the property of transducing energy between the two above-mentioned types; a fluid in said container for acoustical contact with only said inside surface thereof; a piston acting upon said fluid; and means for applying energy of one of said types to said wall portion and for deriving energy of the other of said types therefrom, said last-mentioned means including said electrodes, said piston, and energy-translating means connected to said piston externally of said container and effectively uncoupled from said outside surface thereof for translating the mechanical energy associated with motion of said piston.

16. An electro-mechanical transducer comprising: hollow means having an inside surface and an outside surface defining walls the major portions of which are of polycrystalline dielectric material of the type capable of developing substantial mechanical strains when subjected to electrostatic fields, means for coupling only one of said surfaces effectively to a medium capable of transmitting hydrostatic pressure for translation of acoustical energy between said walls and said medium, and electrode means on each side of said wall portions of said polycrystalline dielectric material for translating the electrical currents associated with the transducing between acoustical energy in said medium and electrical energy in said wall portions.

17. An electro-mechanical transducer comprising: a hollow structure having an inside surface and an outside surface defining walls the major portions of which are of titanate-type polycrystalline dielectric material electrically polarized in directions differing over said wall portions and everywhere substantially normal to one of said surfaces, means for coupling only said one of said surfaces effectively to a medium capable of transmitting acoustical energy for translation of such energy between said one surface and said medium, and electrode means on each side of said wall portions of said polycrystalline dielectric material for translating the electrical currents associated with the transducing between acoustical energy in said medium and electrical energy in said wall portions.

18. An electro-mechanical transducer comprising: inclosing means having an inside surface and an outside surface defining walls the major portions of which are of polycrystalline dielectric material of the type capable of developing sub stantial mechanical strains when subjected to electrostatic fields, means for coupling effectively only one of said two surfaces of said inclosing means to a medium capable of transmitting hydrostatic pressure for translation of acoustical energy between said walls and said medium, and electrode means on said wall portions for translating the electrical currents associated with the transducing between acoustical energy in said medium and electrical energy in said dielectric material.

19. An electro-mechanical transducer comprising: inclosing means having an inside surface and an outside surface defining walls in which, in the event of an application of hydrostatic pressure against only one of said surfaces, such pressure is transformed into stresses in peripheral directions generally parallel to said surfaces, and having at least one substantial portion of said walls composed of polycrystalline dielectric material of the type capable of developing substantial mechanical strains in said peripheral directions when subjected to electrostatic fields; means for coupling effectively only one of said two surfaces to a medium capable of transmitting hydrostatic pressure; and electrode means on said wall portion for translating the electrical currents associated with transducing between mechanical energy in said medium and electrical energy in said wall portion.

ALFRED LESLIE W. WILLIAM-S.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,619,125 Hough Mar. 1, 1927 2,248,870 Langevin July 8, 1941 2,423,459 Mason July 8, 1947 2,447,061 Franklin Aug. 17, 1948 2,486,560 Gray Nov. 1, 1949 FOREIGN PATENTS Number Country Date 583,639 Great Britain Dec. 23, 1946 

